A magnitude 4.1 earthquake broke south of the U.S.-Mexico border, near Guadalupe, Tuesday at 7:57 p.m., causing brief, light shaking in the San Diego area, the US Geological Survey said. The quake occurred in the same area that produced the 7.2 Easter Sunday quake in 2010, and may have been related to that event. USGS placed the epicenter about 59 miles southeast of Octoillo, in a mountainous area.